Thermal coagulation of tissue using RF energy is frequently being used to treat maladies within the body such as liver tumor lesions. Physicians frequently make use of catheter-based RF systems to gain access to interior regions of the body. For treatment of large lesions, the catheter-based RF systems commonly employ needle array-type energy delivery devices. However, depending on the size of the lesion to be ablated and, thus, the size of the array used to ablate the lesion, many conventional systems experience difficulty providing an adequate amount of current to cause tissue heating and coagulation. To address this problem, many manufacturers simply supply a larger generator to provide an adequate amount of current to cause tissue heating and coagulation. Others address the large array problem by having the user step deploy their array at a measured and stable rate. In such a procedure, the physician must carefully apply ablating energy to the element for transmission to the tissue to be ablated, at each predetermined distance, for a fixed period of time and/or until the tissue reaches a desired temperature. A heated center is created as a result, which further heats the target region when the array is fully deployed. This manual procedure tends to be confusing because of the multiple parameters that need to be observed prior to moving on to the next deployment location.
Physicians may experience other difficulties when the lesion to be ablated is close to the dermis or is in tissue that is light in density. When RF catheters or probes are pushed into dense body tissue such as the liver, the probes tend to be inserted deeply enough to remain upright during ablation. However, when ablation procedures, including ablation of some liver lesions, are performed relatively close to the dermis or are performed in tissue that is especially light in density, such as the lung, the physician may have a difficult time maintaining the catheter or probe in its initial orientation. As a result, the physician must either stack pads or gauze under the probe or hold the probe in place during the entire ablation procedure, which is typically about 6–15 minutes. If the physician chooses not to hold or support the probe during such procedures, the probe may sag and could push the energy delivery needles or tines into the dermis layer or other tissue areas not meant to be ablated.
Thus, a need exists for controlling the advancement of the needle array such that the array moves forward to contact new tissue areas once the tissue area presently in contact is ablated. In addition, a need exists for maintaining the probe in a desired orientation for a hands-free mode of operation for the physician.